JP2012034525A - Switching power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply device that can reliably reduce reverse voltage applied to a rectifier element connected to a secondary winding of a transformer and minimize increase of loss as a whole device.SOLUTION: A switching power supply device 1 comprises a transformer 10, a main switching element 120, an active clamp circuit 121, surge suppression circuits 122 and 123, and diodes 130 and 131. The transformer 10 comprises a primary winding 100, a secondary winding 101, and an auxiliary winding 102. Inter-terminal voltage of the auxiliary winding 102 is fixed to battery voltage during non-conductive state of the diode 131 and is fixed to inter-terminal voltage of a capacitor 121a which constitute the active clamp circuit 121 during non-conductive state of the diode 130. This allows the device to reliably reduce the reverse voltage applied to the diodes 130 and 131 connected to the secondary winding 101 of the transformer 10 and minimize increase of loss as the whole device.

Description

  The present invention relates to a switching power supply device including a transformer, a switching element, and a rectifying element.

  Conventionally, as a switching power supply device including a transformer, a switching element, and a rectifying element, for example, there are switching power supply devices disclosed in Patent Literature 1 and Patent Literature 2.

  The switching power supply device of Patent Document 1 includes a transformer, a switch circuit, an output rectifier circuit, and a snubber circuit. The transformer includes an input winding and an output winding. The switch circuit includes a switching element. The switching element is connected between the input winding and the input terminal. The output rectifier circuit includes an output rectifier diode and a rectifier diode. The output rectifier diode is connected between one end of the output winding and the output terminal. The rectifier diode is connected between the other end of the output winding and the output terminal. The snubber circuit includes a snubber capacitor, a snubber diode, and a snubber inductor. The snubber capacitor and the snubber diode are connected in parallel to the output rectifier diode in a state of being connected in series. The snubber inductor is connected in parallel to the snubber diode.

  This switching power supply device switches the switching element to convert the voltage input to the input terminal into a predetermined voltage and outputs the voltage from the output terminal. When the switching element is switched, a surge voltage is applied as a reverse voltage to the diode constituting the output rectifier circuit. Therefore, a diode with a high reverse breakdown voltage must be used for the output rectifier circuit. However, a snubber circuit is provided, and the surge voltage can be suppressed by the snubber circuit. Therefore, a diode having a low withstand voltage can be used for the output rectifier circuit.

  On the other hand, the switching power supply device of Patent Literature 2 includes a transformer, a bridge circuit, a rectifier circuit, and a surge voltage suppression circuit. The transformer includes a primary side winding and two secondary side windings. The two secondary windings are connected in series. The bridge circuit includes four switching elements. Two switching elements are connected in series to form a switching element pair. The bridge circuit is configured by connecting two pairs of switching elements in parallel, and is connected between the primary winding and the high voltage battery. The rectifier circuit includes two diodes. One diode is connected between one secondary winding and the load. The other diode is connected between the other secondary winding and the load. The surge voltage suppression circuit includes a capacitor and a diode. The capacitor and the diode are connected in parallel. The capacitor and the diode connected in parallel are respectively connected in parallel to the two switching elements constituting one switching element pair.

  This switching power supply device converts a voltage of the high-voltage battery into a predetermined voltage and supplies it to a load by switching a predetermined switching element at a predetermined timing. When the switching element is switched, a surge voltage is applied as a reverse voltage to the diode constituting the rectifier circuit. Therefore, a diode having a high reverse breakdown voltage must be used for the rectifier circuit. However, a surge voltage suppression circuit is provided, and the surge voltage can be suppressed by the surge voltage suppression circuit. Therefore, a diode with a low withstand voltage can be used for the rectifier circuit.

Japanese Patent No. 3400443 JP 2007-60890 A

  By the way, in the switching power supply device of Patent Document 1, when suppressing the surge voltage, a voltage due to LC resonance of the inductor and the capacitor constituting the snubber circuit is applied to the diode as a reverse voltage. Therefore, the reverse voltage applied to the diode cannot be completely suppressed.

  On the other hand, in the switching power supply device of Patent Document 2, although the surge voltage can be completely suppressed by the surge voltage suppression circuit, the discharge loss of the capacitor constituting the surge voltage suppression circuit is newly added. Moreover, the loss of the capacitor increases as the input voltage of the switching power supply increases. Therefore, the loss increases as a whole device.

  The present invention has been made in view of such circumstances, and reliably reduces the reverse voltage applied to the rectifying element connected to the secondary winding of the transformer and suppresses an increase in the loss of the entire device. An object of the present invention is to provide a switching power supply device capable of performing

  Therefore, as a result of intensive research and trial and error to solve this problem, the present inventors have provided an auxiliary winding in the transformer, and fixed the voltage between the terminals of the auxiliary winding, so that the secondary winding It has been found that the voltage across the terminals can be suppressed, the reverse voltage applied to the rectifying element can be reliably reduced, and the increase in the loss of the entire apparatus can be suppressed, and the present invention has been completed.

  That is, the switching power supply device according to claim 1 includes a transformer having a primary winding and a secondary winding, a switching element connected between the primary winding and a DC power supply, a secondary winding, In a switching power supply device including a rectifying element connected to a load, the transformer has an auxiliary winding, and the voltage between the terminals of the auxiliary winding is fixed to a predetermined voltage when the rectifying element is non-conductive. It is characterized by being. According to this configuration, the voltage between the terminals of the secondary winding is applied to the rectifying element as a reverse voltage when the rectifying element is non-conductive. However, at this time, the voltage between the terminals of the auxiliary winding is fixed to a predetermined voltage. Therefore, the voltage between the terminals of the secondary winding can be suppressed. Therefore, the reverse voltage applied to the rectifying element can be reliably reduced. Moreover, since there is no discharge loss of the capacitor as in the prior art, an increase in the loss of the entire apparatus can be suppressed.

  The switching power supply device according to claim 2 is characterized in that the voltage between the terminals of the auxiliary winding is fixed to the voltage of the DC power supply when the rectifying element is non-conductive. According to this configuration, the voltage between the terminals of the auxiliary winding can be reliably fixed to a predetermined voltage.

  The switching power supply device according to claim 3 is configured by connecting a surge suppression capacitor element and a surge suppression rectifier element in parallel, connected in series to the auxiliary winding, and connected in parallel to the DC power supply in a connected state. It has a suppression circuit. According to this configuration, the auxiliary winding can be connected to the DC power source via the surge suppression rectifying element. Therefore, the voltage between the terminals of the auxiliary winding can be reliably fixed to the voltage of the DC power supply.

  The switching power supply device according to claim 4, wherein the rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element is connected between one end of the secondary winding and one end of the load. The second rectifier element is connected between the other end of the secondary winding and one end of the load, and is configured by connecting a clamp capacitor element and a clamp switching element in series, and is connected in parallel to the primary winding. It has an active clamp circuit, and the voltage between the terminals of the auxiliary winding is fixed to the voltage of the DC power supply when the second rectifier element is non-conductive, and the voltage between the terminals of the clamp capacitor element when the first rectifier element is non-conductive It is fixed. According to this configuration, the terminal voltage of the auxiliary winding can be reliably fixed.

  The switching power supply device according to claim 5 is configured by connecting the first surge suppression capacitor element and the first surge suppression rectifier element in parallel, connected in series to the auxiliary winding, and connected in parallel to the DC power supply. The first surge suppression circuit to be connected, the second surge suppression capacitor element and the second surge suppression rectifier element are connected in parallel, the connection point between the auxiliary winding and the first surge suppression circuit, the clamp capacitor element and the clamp And a second surge suppression circuit connected between the connection points of the switching elements. According to this configuration, the auxiliary winding can be connected to the DC power supply via the first surge suppression rectifying element. Further, the auxiliary winding can be connected to the clamp capacitor element via the second surge suppression rectifier element. Therefore, the voltage between the terminals of the auxiliary winding can be reliably fixed to the voltage of the DC power supply or the voltage between the terminals of the clamp capacitor.

  The switching power supply device according to claim 6 is characterized in that the primary winding and the auxiliary winding have the same number of turns. According to this configuration, the terminal voltage of the auxiliary winding can be made the same as the terminal voltage of the first winding. Therefore, the surge suppression rectifying element can be reliably brought into a conductive state.

  In the switching power supply device according to claim 7, the auxiliary winding includes a first auxiliary winding and a second auxiliary winding, the rectifying element includes a first rectifying element and a second rectifying element, The first rectifying element is connected between one end of the secondary winding and one end of the load, and the second rectifying element is connected between the other end of the secondary winding and one end of the load. And an active clamp circuit that is connected in parallel to the primary winding, and the voltage between the terminals of the first auxiliary winding is a DC power source when the second rectifier element is non-conductive. The voltage between the terminals of the second auxiliary winding is fixed to the voltage between the terminals of the clamp capacitor element when the first rectifying element is non-conductive. According to this configuration, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed.

  The switching power supply device according to claim 8 is connected in series to the first auxiliary winding, and connected in series to the DC power supply in a state of being connected in series, and connected in series to the second auxiliary winding. A second surge suppression rectifying element connected in parallel to the clamp capacitor element in a state of being connected in series, a connection point between the first auxiliary winding and the surge suppression circuit, a second auxiliary winding and a second surge suppression rectifying element And a second surge suppression capacitive element connected between the connection points. According to this configuration, the first auxiliary winding can be connected to the DC power supply via the first surge suppression rectifying element. Further, the second auxiliary winding can be connected to the clamp capacitor element via the second surge suppression rectifier element. Therefore, it is possible to reliably fix the voltage between the terminals of the first auxiliary winding to the voltage of the DC power supply and the voltage between the terminals of the second auxiliary winding to the voltage between the terminals of the clamp capacitor.

  The switching power supply device according to claim 9 is characterized in that the primary winding, the first auxiliary winding, and the second auxiliary winding have the same number of turns. According to this configuration, the terminal voltage of the first auxiliary winding and the second auxiliary winding can be made the same as the terminal voltage of the first winding. Therefore, the first surge suppression rectifier element and the second surge suppression rectifier element can be reliably brought into a conductive state.

  In the switching power supply device according to claim 10, the transformer includes a first transformer and a second transformer, and the primary winding, the secondary winding, and the auxiliary winding of the first transformer and the second transformer are respectively The switching elements are connected in series, and are connected between the primary windings of the first transformer and the second transformer connected in series and the DC power supply, and the rectifying elements include the first rectifying element and the second rectifying element. The first rectifier element is connected between one end of the secondary winding of the first transformer and the second transformer connected in series and one end of the load, and the second rectifier element is connected to the first transformer connected in series. Is connected between the other end of the secondary winding of the second transformer and one end of the load, and is configured by connecting a clamp capacitance element and a clamp switching element in series, and the first transformer and the second transformer connected in series. A parallel connection to the primary winding The voltage between the terminals of the auxiliary windings of the first transformer and the second transformer connected in series with the active clamp circuit is fixed to the voltage of the DC power supply when the second rectifier is non-conductive, It is characterized by being fixed to the voltage between the terminals of the clamp capacitor element when non-conducting. According to this configuration, it is possible to reliably fix the voltage between the terminals of the auxiliary windings of the first transformer and the second transformer connected in series.

  The switching power supply device according to claim 11 is configured by connecting a first surge suppression capacitor element and a first surge suppression rectifier element in parallel, and is connected in series to auxiliary windings of a first transformer and a second transformer connected in series. A first transformer connected in series with a first surge suppression circuit connected in parallel to a DC power source in a state of being connected in series, a second surge suppression capacitor element, and a second surge suppression rectifier element. And an auxiliary winding of the second transformer and a connection point of the first surge suppression circuit, and a second surge suppression circuit connected between the connection point of the clamp capacitor element and the clamp switching element. . According to this configuration, the auxiliary windings of the first transformer and the second transformer connected in series via the first surge suppression rectifying element can be connected to the DC power source. Further, the auxiliary windings of the first transformer and the second transformer connected in series via the second surge suppression rectifier element can be connected to the clamp capacitor element. Therefore, the voltage between the terminals of the auxiliary windings of the first transformer and the second transformer connected in series can be reliably fixed to the voltage of the DC power supply or the voltage between the terminals of the clamp capacitor.

  According to a twelfth aspect of the present invention, the number of turns of the primary winding and the auxiliary winding of the first transformer and the second transformer is the same. According to this configuration, the voltage between the terminals of the auxiliary windings of the first transformer and the second transformer connected in series is made equal to the voltage between the terminals of the first windings of the first transformer and the second transformer connected in series. be able to. Therefore, the first surge suppression rectifier element and the second surge suppression rectifier element can be reliably brought into a conductive state.

  In the switching power supply device according to claim 13, the transformer includes a first transformer and a second transformer, the auxiliary winding includes a first auxiliary winding and a second auxiliary winding, and the first transformer And the primary winding, the secondary winding, the first auxiliary winding, and the second auxiliary winding of the second transformer are connected in series, and the switching element is one of the first transformer and the second transformer connected in series. The rectifying element is composed of a first rectifying element and a second rectifying element. The first rectifying element is connected between the first transformer and the second transformer connected in series. The second rectifying element is connected between one end of the secondary winding and one end of the load, and the second rectifying element is connected between the other end of the secondary winding of the first transformer and the second transformer connected in series and one end of the load. The clamp capacitor and clamp switching element are connected in series. An active clamp circuit connected in parallel to the primary winding of the first transformer and the second transformer connected in series, between the terminals of the first auxiliary winding of the first transformer and the second transformer connected in series The voltage is fixed to the voltage of the DC power supply when the second rectifying element is non-conductive, and the voltage between the terminals of the first transformer and the second auxiliary winding of the second transformer connected in series is non-conductive to the first rectifying element. Sometimes it is fixed to the voltage between terminals of the clamp capacitor. According to this configuration, the voltage across the terminals of the first auxiliary winding of the first transformer and the second transformer connected in series and the second auxiliary winding of the first transformer and the second transformer connected in series are securely fixed. be able to.

  The switching power supply device according to claim 14 is configured by connecting the first surge suppression capacitor element and the first surge suppression rectifier element in parallel, and the first auxiliary winding of the first transformer and the second transformer connected in series. In a state of being connected in series and connected in series to a surge suppression circuit connected in parallel to a DC power source in a state of being connected in series and a second auxiliary winding of a first transformer and a second transformer connected in series A second surge suppression rectifier connected in parallel to the clamp capacitor, a first transformer connected in series, a first auxiliary winding of the second transformer, a connection point of a surge suppression circuit, and a first transformer connected in series And a second surge suppression capacitor element connected between the second auxiliary winding of the second transformer and the connection point of the second surge suppression rectifier element. According to this configuration, the first auxiliary winding of the first transformer and the second transformer connected in series via the first surge suppression rectifying element can be connected to the DC power source. In addition, the first transformer and the second auxiliary winding of the second transformer connected in series via the second surge suppression rectifier element can be connected to the clamp capacitor element. Therefore, the voltage between the terminals of the first auxiliary winding of the first transformer and the second transformer connected in series is set to the voltage of the DC power supply, and the voltage between the terminals of the second auxiliary winding of the first transformer and the second transformer connected in series. The voltage can be reliably fixed to the voltage between the terminals of the clamp capacitor.

  According to a fifteenth aspect of the present invention, the number of turns of the primary winding, the first auxiliary winding, and the second auxiliary winding of the first transformer and the second transformer is the same. According to this configuration, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding of the first transformer and the second transformer connected in series is changed to the first winding of the first transformer and the second transformer connected in series. It can be the same as the voltage across the wires. Therefore, the first surge suppression rectifier element and the second surge suppression rectifier element can be reliably brought into a conductive state.

  The switching power supply device according to claim 16, wherein the secondary winding includes a first secondary winding and a second secondary winding, and the first secondary winding and the second secondary winding. The windings are connected in series, the auxiliary winding is composed of a first auxiliary winding and a second auxiliary winding, the rectifier element is composed of a first rectifier element and a second rectifier element, and the first rectifier The element is connected between one end of the first secondary winding and one end of the load, and the second rectifying element is connected between one end of the second secondary winding and one end of the load, At least one of the voltages between the terminals of the first auxiliary winding and the second auxiliary winding is fixed to the voltage of the DC power supply when the first rectifying element and the second rectifying element are non-conductive. According to this configuration, at least one of the inter-terminal voltages of the first auxiliary winding and the second auxiliary winding can be reliably fixed.

  In the switching power supply device according to claim 17, the switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power supply in a state of being connected in series. The third switching element and the fourth switching element are connected in parallel to the DC power source in a state of being connected in series, and the primary winding is a connection point between the first switching element and the second switching element, and the third switching element, A first surge-suppressing rectifier element connected between a connection point of the fourth switching element, connected in series to the first auxiliary winding, and connected in parallel to the first switching element in a state of being connected in series; and a second auxiliary A second surge suppression rectifier element connected in series to the winding and connected in parallel to the second switching element in a state of being connected in series; the first auxiliary winding; and the first And having a connection point of the over-di inhibiting the rectifying element, and a surge suppression capacitor element connected between a connection point of the second auxiliary winding and the second surge suppression rectifying element. According to this configuration, the first auxiliary winding can be connected to the DC power source via the second switching element and the first surge suppression rectifying element. The second auxiliary winding can be connected to the DC power source via the first switching element and the second surge suppression rectifying element. Therefore, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed to the voltage of the DC power source.

  In the switching power supply device according to claim 18, the switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power supply in a state of being connected in series. The third switching element and the fourth switching element are connected in parallel to the DC power source in a state of being connected in series, and the primary winding is a connection point between the first switching element and the second switching element, and the third switching element, A first surge-suppressing rectifying element connected between a connection point of the fourth switching element, connected in series to the first auxiliary winding, and connected in parallel to the DC power source in a state of being connected in series; and a second auxiliary winding The second surge suppression rectifying element connected in series to the DC power source in a state of being connected in series, and the connection of the first auxiliary winding and the first surge suppression rectifying element When, and having a surge suppression capacitor element connected between a connection point of the second auxiliary winding and the second surge suppression rectifying element. According to this configuration, the first auxiliary winding can be connected to the DC power supply via the first surge suppression rectifying element. The second auxiliary winding can be connected to the DC power source via the second surge suppressing rectifying element. Therefore, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed to the voltage of the DC power source.

  In the switching power supply device according to claim 19, the switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power supply in a state of being connected in series. The third switching element and the fourth switching element are connected in parallel to the DC power source in a state of being connected in series, and the primary winding is a connection point between the first switching element and the second switching element, and the third switching element, A first surge-suppressing rectifier element connected between a connection point of the fourth switching element, connected in series to the first auxiliary winding, and connected in parallel to the fourth switching element in a connected state; and a second auxiliary A second surge suppression rectifier element connected in series to the winding and connected in parallel to the second switching element in a state of being connected in series; the first auxiliary winding; and the first And having a connection point of the over-di inhibiting the rectifying element, and a surge suppression capacitor element connected between a connection point of the second auxiliary winding and the second surge suppression rectifying element. According to this configuration, the first auxiliary winding can be connected to the DC power supply via the third switching element and the first surge suppression rectifying element. The second auxiliary winding can be connected to the DC power source via the first switching element and the second surge suppression rectifying element. Therefore, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed to the voltage of the DC power source.

  In the switching power supply device according to claim 20, the switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power supply in a state of being connected in series. The third switching element and the fourth switching element are connected in parallel to the DC power source in a state of being connected in series, and the primary winding is a connection point between the first switching element and the second switching element, and the third switching element, A first surge-suppressing rectifying element connected between a connection point of the fourth switching element, connected in series to the first auxiliary winding, and connected in parallel to the DC power source in a state of being connected in series; and a second auxiliary winding A second surge suppression rectifier element connected in series to the second switching element in a series connected state, a first auxiliary winding, and a first surge suppression regulator And having a connection point of the element, and a surge suppression capacitor element connected between a connection point of the second auxiliary winding and the second surge suppression rectifying element. According to this configuration, the first auxiliary winding can be connected to the DC power supply via the first surge suppression rectifying element. The second auxiliary winding can be connected to the DC power source via the second switching element and the second surge suppression rectifying element. Therefore, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed to the voltage of the DC power source.

  In the switching power supply device according to claim 21, the switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power supply in a state of being connected in series. The third switching element and the fourth switching element are connected in parallel to the DC power source in a state of being connected in series, and the primary winding is a connection point between the first switching element and the second switching element, and the third switching element, A first surge suppression capacitor element and a second surge suppression capacitor element that are connected between the connection points of the fourth switching elements and connected in parallel to the DC power supply in a state of being connected in series, and connected in series to the first auxiliary winding And connected in series to the first surge suppression rectifier element connected in parallel to the first surge suppression capacitor element in series connected to the second auxiliary winding. A second surge suppression rectifying element connected in parallel to the second surge suppression capacitive element in a connected state; a connection point between the first auxiliary winding and the first surge suppression rectifying element; a second auxiliary winding and a second surge; And a surge suppression capacitor element connected between the connection points of the suppression rectifier elements. According to this configuration, the first auxiliary winding can be connected to the first surge suppression capacitor element via the first surge suppression rectifier element. The second auxiliary winding can be connected to the second surge suppression capacitor element via the second surge suppression rectifier element. Therefore, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be reliably fixed to a predetermined voltage.

  The switching power supply device according to claim 22 is characterized in that the primary winding, the first auxiliary winding, and the second auxiliary winding have the same number of turns. According to this configuration, in the switching power supply device according to any one of claims 17 to 20, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be made the same as the voltage between the terminals of the first winding. . Therefore, the first surge suppression rectifier element and the second surge suppression rectifier element can be reliably brought into a conductive state.

The switching power supply device according to claim 23, wherein the number of turns of the first auxiliary winding and the second auxiliary winding is
The number of turns of the primary winding is 1/2. According to this configuration, in the switching power supply device according to claim 21, the voltage between the terminals of the first auxiliary winding and the second auxiliary winding can be made the same as the voltage between the terminals of the first winding. Therefore, the first surge suppression rectifier element and the second surge suppression rectifier element can be reliably brought into a conductive state.

  According to a twenty-fourth aspect of the present invention, the switching power supply device is mounted on a vehicle and supplies voltage to the electronic device. According to this configuration, in the switching power supply device that is mounted on the vehicle and supplies the voltage to the electronic device, the reverse voltage applied to the rectifying element connected to the secondary winding of the transformer is reliably reduced, and the entire device is The increase in loss can also be suppressed.

It is a circuit diagram of the DC-DC converter in a 1st embodiment. It is a waveform of each part of the DC-DC converter shown in FIG. It is a circuit diagram of the DC-DC converter in 2nd Embodiment. It is a circuit diagram of the DC-DC converter in 3rd Embodiment. It is a circuit diagram of the DC-DC converter in 4th Embodiment. It is a circuit diagram of the DC-DC converter in 5th Embodiment. It is a circuit diagram of the DC-DC converter in 6th Embodiment. It is a waveform of each part of the DC-DC converter shown in FIG. It is a circuit diagram of the DC-DC converter in 7th Embodiment. It is a circuit diagram of the DC-DC converter in the modification of 7th Embodiment. It is a circuit diagram of the DC-DC converter in another modification of 7th Embodiment. It is a circuit diagram of the DC-DC converter in 8th Embodiment.

  Next, an embodiment is given and this invention is demonstrated in detail. In this embodiment, an example in which the switching power supply device according to the present invention is applied to a DC-DC converter that is mounted on a vehicle and that steps down the voltage of a battery and supplies the voltage to an electronic device is shown.

(First embodiment)
First, the configuration of the DC-DC converter will be described with reference to FIG. Here, FIG. 1 is a circuit diagram of the DC-DC converter of the first embodiment. Note that the symbol “·” attached to the primary winding 100, the secondary winding 101, and the auxiliary winding 102 of the transformer 10 indicates the start of winding of the winding.

  The DC-DC converter 1 (switching power supply device) shown in FIG. 1 insulates and steps down the DC voltage output from the battery B1 (DC power supply) and supplies it to the electronic device S1 (load) mounted on the vehicle. It is a forward type converter. The DC-DC converter 1 includes a transformer 10, a coil 11, an input side circuit 12, an output side circuit 13, and a control circuit 14.

  The transformer 10 is an element that steps down an alternating voltage input to the primary side and outputs it from the secondary side. The transformer 10 includes a primary winding 100, a secondary winding 101, and an auxiliary winding 102. The number of turns of the primary winding 100 is set to Np. The number of turns of the secondary winding 101 is set to Ns smaller than the number of turns Np of the primary winding 100. The number of turns of the auxiliary winding 102 is set to the same Np as the number of turns of the primary winding 100. One end of the primary winding 100 on the winding start side is connected to the coil 11 and the other end is connected to the input side circuit 12. One end and the other end on the winding start side of the secondary winding 101 are connected to the output side circuit 13, respectively. One end on the winding start side of the auxiliary winding 102 is connected to the positive end of the battery B1, and the other end is connected to a component of the input side circuit 12 described later.

  The coil 11 is an element that stores and discharges energy when a current flows. The coil 11 is connected in series with the primary winding 100. One end of the coil 11 is connected to one end of the primary winding 100, and the other end is connected to the positive end of the battery B1.

  The input side circuit 12 is a circuit that converts a DC voltage output from the battery B1 into an AC voltage. The input side circuit 12 includes a main switching element 120 (switching element), an active clamp circuit 121, a surge suppression circuit 122 (first surge suppression circuit), 123 (second surge suppression circuit), and an auxiliary winding 102. I have.

  The main switching element 120 is an element that is connected between the primary winding 100 and the battery B1, and controls the voltage supplied from the battery B1 to the primary winding 100 by switching. The main switching element 120 is, for example, a MOSFET. The drain of the main switching element 120 is connected to the other end of the primary winding 100, and the source is connected to the negative end of the battery B1.

  The active clamp circuit 121 is a circuit that is connected in parallel to the primary winding 100 and resets the transformer 10 while the main switching element 120 is off. The active clamp circuit 121 includes a capacitor 121a (clamp capacitance element) and a sub switching element 121b (clamp switching element). The sub switching element 121b is, for example, a MOSFET. The capacitor 121a and the sub switch 121b are connected in series. Specifically, the capacitor 121a is connected to the drain of the sub switching element 121b. One end of the capacitor 121 a is connected to the other end of the coil 11. The source of the sub switching element 121 b is connected to the other end of the primary winding 100. The gate is connected to the control circuit 14. The active clamp circuit 121 is connected in parallel to the primary winding 100 via the coil 11.

  The surge suppression circuits 122 and 123 are circuits that suppress a surge voltage that is generated when the main switching element 120 and the sub switching element 121b are switched.

  The surge suppression circuit 122 includes a capacitor 122a (first surge suppression capacitance element) and a diode 122b (first surge suppression rectifier element). The capacitor 122a is connected in parallel to the diode 122b. The cathode of the diode 122b is connected to the other end of the auxiliary winding 102, and the anode is connected to the negative end of the battery B1. The surge suppression circuit 122 is connected in series to the auxiliary winding 102, and is connected in parallel to the battery B1 in a state of being connected in series.

  The surge suppression circuit 123 includes a capacitor 123a (second surge suppression capacitance element) and a diode 123b (second surge suppression rectifier element). The capacitor 123a is connected in parallel to the diode 123b. The cathode of the diode 123b is connected to the connection point between the capacitor 121a and the sub-switching element 121b, and the anode is connected to the connection point between the auxiliary winding 102 and the surge suppression circuit 122.

  The output side circuit 13 is connected between the transformer 10 and the electronic device S1, and is a circuit that rectifies an AC voltage output from the transformer 10 to convert it into a DC voltage and supplies the DC voltage to the electronic device S1. The output side circuit 13 includes diodes 130 (first rectifier elements) and 131 (second rectifier elements), a coil 132, and a capacitor 133.

  The diodes 130 and 131 are elements that rectify the AC voltage output from the secondary winding 101.

  The diode 130 is connected between one end of the secondary winding 101 and the positive end of the electronic device S1. The anode of the diode 130 is connected to one end of the secondary winding 101. Further, the cathode is connected to the coil 132, and is connected to the positive electrode end of the electronic device S1 through the coil 132.

  The diode 131 is connected between the other end of the secondary winding 101 and the positive end of the electronic device S1. The anode of the diode 131 is connected to the other end of the secondary winding 101. Further, the cathode is connected to the coil 132, and is connected to the positive electrode end of the electronic device S1 through the coil 132.

  The coil 132 is an element that stores and discharges energy when a current flows. One end of the coil 132 is connected to the cathodes of the diodes 130 and 131, and the other end is connected to the positive terminal of the electronic device S1.

  The capacitor 133 is an element that smoothes the DC voltage rectified by the diodes 130 and 131. One end of the capacitor 133 is connected to the other end of the coil 132 connected to the positive terminal of the electronic device S1. The other end is connected to the other end of the secondary winding 101 connected to the negative electrode end of the electronic device S1.

  The control circuit 14 is a circuit that controls the switching of the main switching element 120 and the sub switching element 121b so that the output voltage becomes the target voltage. The control circuit 14 is connected to the gates of the main switching element 120 and the sub switching element 121b.

  Next, the operation of the DC-DC converter will be described with reference to FIGS. Here, FIG. 2 is a waveform of each part of the DC-DC converter shown in FIG. Note that the DC-DC converter 1 is a one-stone forward converter as described above, and the voltage conversion operation is well known, and thus the description thereof is omitted. Here, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described.

  When the main switching element 120 shown in FIG. 1 is turned on and the sub switching element 121b is turned off, the diode 130 is turned on and the diode 131 is turned off. As shown in FIG. 2, the forward current flowing through the diode 130 increases and the forward current flowing through the diode 131 decreases (t0 to t1). When the forward current flowing through the diode 131 becomes 0 (t1), the diode 131 enters a reverse recovery period. However, the capacitors 122a and 123a and the coil 11 suppress a steep voltage change at the time of reverse recovery by the resonance operation. Therefore, the generation of noise can be suppressed.

  When the energy accumulated in the capacitor 122a is transferred to the coil 11 due to the resonance operation, the diode 122b becomes conductive (t2 to t3). The auxiliary winding 102 is connected to the battery B1 via the diode 122b. As a result, the voltage between the terminals of the auxiliary winding 102 is fixed to the voltage of the battery B1. Therefore, the voltage between the terminals of the secondary winding 101 is fixed to a predetermined voltage determined by the voltage of the battery B1 and the turn ratio of the transformer 10. Therefore, the reverse voltage applied to the diode 131 can be suppressed to a predetermined voltage determined by the voltage of the battery B1 and the turn ratio. At this time, the current flowing through the auxiliary winding 102 flows back through the coil 11, the primary winding 100, the main switching element 120, and the diode 122b. The energy stored in the capacitor 122a is finally transferred to the output side circuit 13 via the transformer 10.

  When the main switching element shown in FIG. 1 is turned off and the sub switching element 121b is turned on, the diode 130 is turned off and the diode 131 is turned on, contrary to the previous case. As shown in FIG. 2, the forward current flowing through the diode 130 decreases, and the forward current flowing through the diode 131 increases (t4 to t5). When the forward current flowing through the diode 130 becomes 0 (t5), the diode 130 enters a reverse recovery period. However, the capacitors 122a and 123a and the coil 11 suppress a steep voltage change at the time of reverse recovery by the resonance operation. Therefore, the generation of noise can be suppressed.

  When the energy accumulated in the capacitor 123a is transferred to the coil 11 due to the resonance operation, the diode 123b becomes conductive (t6 to t7). The auxiliary winding 102 is connected to the capacitor 121a through the diode 123b. As a result, the terminal voltage of the auxiliary winding 102 is fixed to the terminal voltage of the capacitor 121a. Here, the inter-terminal voltage of the capacitor 121a is a predetermined voltage determined by the voltage of the battery B1, the winding ratio of the transformer 10, and the on-duty ratio of the main switching element 120. Therefore, the voltage between the terminals of the secondary winding 101 is fixed to a predetermined voltage determined by the voltage of the battery B1, the turn ratio, and the on-duty ratio. Therefore, the reverse voltage applied to the diode 130 can be suppressed to a predetermined voltage determined by the voltage of the battery B1, the winding ratio, and the on-duty ratio. At this time, the current flowing through the auxiliary winding 102 flows back through the diode 123b, the sub switching element 121b, the primary winding 100, and the coil 11. The energy stored in the capacitor 123a is finally regenerated in the battery B1.

  Next, the effect will be described. According to the first embodiment, the voltage between the terminals of the secondary winding 101 is applied to the diode 130 as a reverse voltage when the diode 130 is not conducting. In addition, when the diode 131 is not conducting, the voltage across the secondary winding 101 is applied to the diode 131 as a reverse voltage. However, at this time, the voltage between the terminals of the auxiliary winding 102 is fixed to a predetermined voltage. Therefore, the voltage between the terminals of the secondary winding can be suppressed. Therefore, the reverse voltage applied to the diodes 130 and 131 can be reliably suppressed in the DC-DC converter 1 that is mounted on the vehicle and supplies a voltage to the electronic device. Moreover, since there is no discharge loss of the capacitor as in the prior art, an increase in the loss of the entire apparatus can be suppressed.

  Further, according to the first embodiment, the terminal voltage of the auxiliary winding 102 is fixed to the voltage of the battery B1 or the terminal voltage of the capacitor 121a. Therefore, the voltage between the terminals of the auxiliary winding 102 can be reliably fixed to a predetermined voltage.

  Furthermore, according to the first embodiment, the auxiliary winding 102 is connected to the battery B1 via the diode 122b. Further, the auxiliary winding 102 is connected to the capacitor 121a via the diode 123b. Therefore, the voltage between the terminals of the auxiliary winding 102 can be reliably fixed to the voltage of the battery B1 or the voltage between the terminals of the capacitor 121a.

  In addition, according to the first embodiment, the number of turns of the primary winding 100 and the auxiliary winding 102 is set to be the same. Thereby, the inter-terminal voltage of the auxiliary winding 102 can be made the same as the inter-terminal voltage of the first winding 100. Therefore, the diodes 122b and 123b can be reliably turned on.

(Second Embodiment)
Next, the DC-DC converter of the second embodiment will be described. The DC-DC converter of the second embodiment is configured to have two auxiliary windings, whereas the DC-DC converter of the first embodiment is configured to have one auxiliary winding. .

  First, the configuration of the DC-DC converter of the second embodiment will be described with reference to FIG. Here, FIG. 3 is a circuit diagram of the DC-DC converter in the second embodiment. Note that the symbol “·” attached to the primary winding 200, the secondary winding 201, and the auxiliary winding 202 of the transformer 20 indicates the start of winding of the winding.

  The DC-DC converter 2 (switching power supply device) shown in FIG. 3 is a one-stone forward converter. The DC-DC converter 2 includes a transformer 20, a coil 21, an input side circuit 22, an output side circuit 23, and a control circuit 24. The coil 21, the output side circuit 23, and the control circuit 24 have the same configuration as the coil 11, the output side circuit 13, and the control circuit 14 of the first embodiment.

  The transformer 20 includes a primary winding 200, a secondary winding 201, and auxiliary windings 202 (first auxiliary winding) and 203 (second auxiliary winding). The primary winding 200, the secondary winding 201, and the auxiliary winding 202 have the same configuration as the primary winding 100, the secondary winding 101, and the auxiliary winding 102 of the first embodiment. The number of turns of the auxiliary winding 203 is set to the same Np as the number of turns of the primary winding 200. The auxiliary winding 203 is connected to each component of the input side circuit 22.

  The input side circuit 22 includes a main switching element 220 (switching element), an active clamp circuit 221, a surge suppression diode 222b (first surge suppression rectification element), a surge suppression diode 224 (second surge suppression rectification element), A surge suppression capacitor 225 (second surge suppression capacitor) and auxiliary windings 202 and 203 are provided. The main switching element 220 and the active clamp circuit 221 have the same configuration as the main switching element 120 and the active clamp circuit 121 of the first embodiment.

  The surge suppression diode 224 and the surge suppression capacitor 225 are elements that suppress a surge voltage that is generated when the main switching element 220 and the sub switching element 221b are switched.

  The surge suppression diode 224 is DC connected to the auxiliary winding 203. Specifically, the cathode of the surge suppression diode 224 is connected to one end on the winding start side of the auxiliary winding 203. The anode of the surge suppression diode 224 is connected to one end of the capacitor 221a. The other end of the auxiliary winding 203 is connected to the other end of the capacitor 221a. The surge suppression diode 224 and the auxiliary winding 203 connected in series are connected in parallel to the capacitor 221a.

  One end of the surge suppression capacitor 225 is connected to a connection point between the auxiliary winding 202 and the surge suppression diode 222b, and the other end is connected to a connection point between the auxiliary winding 203 and the surge suppression diode 224.

  Next, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described with reference to FIG. When the diode 230 is turned on and the diode 231 is turned off, the auxiliary winding 202 is connected to the battery B2 through the surge suppression diode 222b. As a result, the terminal voltage of the auxiliary winding 202 is fixed to the voltage of the battery B2. Therefore, the voltage between the terminals of the secondary winding 201 is fixed to a predetermined voltage determined by the voltage of the battery B2 and the turn ratio of the transformer 20. Therefore, the reverse voltage applied to the diode 231 can be suppressed to a predetermined voltage determined by the voltage of the battery B2 and the turn ratio.

  When the diode 230 is turned off and the diode 231 is turned on, the auxiliary winding 203 is connected to the capacitor 221a via the diode 224. As a result, the terminal voltage of the auxiliary winding 203 is fixed to the terminal voltage of the capacitor 221a. Therefore, the voltage between the terminals of the secondary winding 201 is fixed to a predetermined voltage determined by the voltage between the terminals of the capacitor 221a, the turns ratio of the transformer 20, and the on-duty ratio of the main switching element 220. Therefore, the reverse voltage applied to the diode 230 can be suppressed to a predetermined voltage determined by the voltage between the terminals of the capacitor 221a, the turn ratio, and the on-duty ratio.

  Next, the effect will be described. According to the second embodiment, the voltage between the terminals of the auxiliary windings 202 and 203 is fixed to the voltage of the battery B2 or the voltage between the terminals of the capacitor 221a. Therefore, the voltage between the terminals of the auxiliary winding 202 can be reliably fixed to a predetermined voltage.

  Further, according to the second embodiment, the auxiliary winding 202 is connected to the battery B2 via the surge suppression diode 222b. Further, the auxiliary winding 203 is connected to the capacitor 221a through the diode 224. Therefore, the voltage between the terminals of the auxiliary windings 202 and 203 can be reliably fixed to the voltage of the battery B2 or the voltage between the terminals of the capacitor 221a.

  Furthermore, according to the second embodiment, the primary winding 200 and the auxiliary windings 202 and 203 are set to have the same number of turns. Thereby, the voltage between the terminals of the auxiliary windings 202 and 203 can be made the same as the voltage between the terminals of the first winding 200. Therefore, the surge suppression diodes 222b and 224 can be reliably turned on.

(Third embodiment)
Next, a DC-DC converter according to a third embodiment will be described. The DC-DC converter of the third embodiment is configured to have two transformers, whereas the DC-DC converter of the first embodiment is configured to have one transformer, and accordingly the output side The circuit configuration is changed.

  First, the configuration of the DC-DC converter of the third embodiment will be described with reference to FIG. Here, FIG. 4 is a circuit diagram of the DC-DC converter in the third embodiment. In addition, the symbol “·” attached to the primary windings 300A and 300B, the secondary windings 301A and 301B, and the auxiliary windings 302A and 302B of the transformers 30A and 30B indicates the beginning of winding.

  The DC-DC converter 3 (switching power supply device) shown in FIG. 4 is a one-stone forward flyback converter. The DC-DC converter 3 includes transformers 30A (first transformer) and 30B (second transformer), a coil 31, an input side circuit 32, an output side circuit 33, and a control circuit 34. The coil 31 and the control circuit 34 have the same configuration as the coil 11 and the control circuit 14 of the first embodiment.

  The transformers 30A and 30B include primary windings 300A and 300B, secondary windings 301A and 301B, and auxiliary windings 302A and 302B (auxiliary windings). The number of turns of the primary windings 300A and 300B is set to Np. The number of turns of the secondary windings 301A and 301B is set to Ns smaller than the number of turns Np of the primary windings 300A and 300B. The number of turns of the auxiliary windings 302A and 302B is set to the same Np as the number of turns of the primary windings 300A and 300B. The primary windings 300A and 300B, the secondary windings 301A and 301B, and the auxiliary windings 302A and 302B are connected in series, respectively. The primary windings 300A and 300B connected in series correspond to the primary winding 100 of the first embodiment. The auxiliary windings 302A and 302B connected in series correspond to the auxiliary winding 102 of the first embodiment. One end on the winding start side of the primary winding 300A is connected to the positive end of the battery B3, and one end on the winding end side of the primary winding 300B is connected to the input side circuit 32. One end on the winding start side of the secondary winding 301A and one end on the winding end side of the secondary winding 301B are connected to the output side circuit 33, respectively. One end on the winding start side of the auxiliary winding 302A is connected to the positive end of the battery B3, and one end on the winding end side of the auxiliary winding 302B is connected to the components of the input side circuit 32.

  The input side circuit 32 includes a main switching element 320 (switching element), an active clamp circuit 321, a surge suppression circuit 322 (first surge suppression circuit), 322 (second surge suppression circuit), and auxiliary windings 302A and 302B. And. If the auxiliary windings 302A and 302B connected in series are regarded as the auxiliary winding 102 of the first embodiment, the input side circuit 32 has the same configuration as the input side circuit 12 of the first embodiment.

The output side circuit 33 includes a diode 334 (first rectifier element), 335 (second rectifier element),
And a capacitor 333.

  The diode 334 is connected between one end of the secondary windings 301A and 301B connected in series and the positive end of the electronic device S3. The anode of the diode 334 is connected to one end on the winding start side of the secondary winding 301A. The cathode is connected to the positive terminal of the electronic device S3.

  The diode 335 is connected between the other ends of the secondary windings 301A and 301B connected in series and the positive end of the electronic device S3. The anode of the diode 335 is connected to one end on the winding end side of the secondary winding 301B. The cathode is connected to the positive terminal of the electronic device S3.

  One end of the capacitor 333 is connected to the cathodes of the diodes 334 and 335 connected to the positive terminal of the electronic device S3. The other end is connected to a connection point of the secondary windings 301A and 301B connected to the negative electrode end of the electronic device S3.

  Next, the operation of the DC-DC converter will be described with reference to FIG. Note that the DC-DC converter 3 is a one-stone forward flyback converter as described above, and the voltage conversion operation is well known, and thus the description thereof is omitted. Here, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described. When the diode 334 is turned on and the diode 335 is turned off, the auxiliary windings 302A and 302B connected in series are connected to the battery B3 via the diode 322b. As a result, the voltage between the terminals of the auxiliary windings 302A and 302B connected in series is fixed to the voltage of the battery B3. Therefore, the voltage between the terminals of the secondary windings 301A and 301B connected in series is fixed to a predetermined voltage determined by the voltage of the battery B3 and the turn ratio of the transformer 30. Therefore, the reverse voltage applied to the diode 335 can be suppressed to a predetermined voltage determined by the voltage of the battery B3 and the turn ratio.

  When the diode 334 is non-conductive and the diode 335 is conductive, the auxiliary windings 302A and 302B connected in series are connected to the capacitor 321a via the diode 323b. As a result, the terminal voltage of the auxiliary windings 302A and 302B connected in series is fixed to the terminal voltage of the capacitor 321a. Therefore, the voltage between the terminals of the secondary windings 301A and 301B connected in series is fixed to a predetermined voltage determined by the voltage between the terminals of the capacitor 321a, the turn ratio of the transformer 30, and the on-duty ratio of the main switching element 320. Will be. Therefore, the reverse voltage applied to the diode 334 can be suppressed to a predetermined voltage determined by the voltage between the terminals of the capacitor 321a, the turn ratio, and the on-duty ratio.

  Next, the effect will be described. According to the third embodiment, the voltage between the terminals of the auxiliary windings 302A and 302B connected in series is fixed to the voltage of the battery B3 or the voltage between the terminals of the capacitor 321a. Therefore, the voltage between the terminals of the auxiliary windings 302A and 302B connected in series can be reliably fixed to a predetermined voltage.

  Further, according to the third embodiment, the auxiliary windings 302A and 302B connected in series via the diode 322b are connected to the battery B3. Further, the auxiliary windings 302A and 302B connected in series via the diode 323b are connected to the capacitor 321a. Therefore, the voltage between the terminals of the auxiliary windings 302A and 302B connected in series can be reliably fixed to the voltage of the battery B3 or the voltage between the terminals of the capacitor 321a.

  Furthermore, according to the third embodiment, the primary windings 300A and 300B and the auxiliary windings 302A and 302A are set to have the same number of turns. Thereby, the voltage between the terminals of the auxiliary windings 301A and 301B connected in series can be made the same as the voltage between the terminals of the first windings 300A and 300B connected in series. Therefore, the diodes 322b and 323b can be reliably turned on.

(Fourth embodiment)
Next, a DC-DC converter according to a fourth embodiment will be described. The DC-DC converter according to the fourth embodiment is configured to have two transformers, whereas the DC-DC converter according to the second embodiment is configured to have one transformer. The circuit configuration is changed to the same configuration as that of the third embodiment.

  First, the configuration of the DC-DC converter of the fourth embodiment will be described with reference to FIG. Here, FIG. 5 is a circuit diagram of the DC-DC converter in the fourth embodiment. Note that the symbol “·” attached to the primary windings 400A and 400B, the secondary windings 401A and 401B, and the auxiliary windings 402A, 402B, 403A, and 403B of the transformers 40A and 40B indicates the winding start of the windings.

  The DC-DC converter 4 (switching power supply device) shown in FIG. 5 is a one-stone forward flyback converter. The DC-DC converter 4 includes transformers 40A and 40B, a coil 41, an input side circuit 42, an output side circuit 43, and a control circuit 44. The coil 41 and the output side circuit 43 have the same configuration as the coil 31 and the output side circuit 33 of the third embodiment. The control circuit 44 has the same configuration as the control circuit 24 of the second embodiment.

  The transformers 40A and 40B include primary windings 400A and 400B, secondary windings 401A and 401B, auxiliary windings 402A and 402B (first auxiliary winding), and auxiliary windings 403A and 403B (second auxiliary winding). Line). The number of turns of the primary windings 400A and 400B is set to Np. The number of turns of the secondary windings 401A and 401B is set to Ns smaller than the number of turns Np of the primary windings 400A and 400B. The number of turns of the auxiliary windings 402A, 402B, 403A, 403B is set to the same Np as the number of turns of the primary windings 400A, 400B. Primary windings 400A and 400B, secondary windings 401A and 401B, auxiliary windings 402A and 402B, and auxiliary windings 403A and 403B are connected in series, respectively. The primary windings 400A and 400B connected in series correspond to the primary winding 200 of the second embodiment. The auxiliary windings 402A and 402B connected in series correspond to the auxiliary winding 202 of the second embodiment. The auxiliary windings 403A and 403B connected in series correspond to the auxiliary winding 203 of the second embodiment. One end on the winding start side of the primary winding 400A is connected to the positive end of the battery B4, and one end on the winding end side of the primary winding 400B is connected to the input side circuit 42. One end on the winding start side of the secondary winding 401A and one end on the winding end side of the secondary winding 401B are connected to the output side circuit 43, respectively. The auxiliary windings 403 </ b> A and 403 </ b> B connected in series are connected to the components of the input side circuit 42.

  The input side circuit 42 includes a main switching element 420 (switching element), an active clamp circuit 421, a surge suppression circuit 422, a surge suppression diode 424 (second surge suppression rectifier element), and a surge suppression capacitor 425 (second surge). Suppression capacitor) and auxiliary windings 402A and 402B (first auxiliary winding), 403A and 403B (second auxiliary winding). If the auxiliary windings 402A and 402B connected in series are regarded as the auxiliary winding 202 of the second embodiment and the auxiliary windings 403A and 403B connected in series are the auxiliary winding 203 of the second embodiment, the input side circuit 42 These have the same configuration as the input side circuit 22 of the second embodiment.

  Next, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described with reference to FIG. When the diode 434 is turned on and the diode 435 is turned off, the auxiliary windings 402A and 402B connected in series are connected to the battery B4 via the diode 422b. As a result, the voltage between the terminals of the auxiliary windings 402A and 402B connected in series is fixed to the voltage of the battery B4. Therefore, the voltage between the terminals of the secondary windings 401A and 401B connected in series is fixed to a predetermined voltage determined by the voltage of the battery B4 and the turn ratio of the transformer 40. Therefore, the reverse voltage applied to the diode 435 can be suppressed to a predetermined voltage determined by the voltage of the battery B4 and the turn ratio.

  When the diode 434 is turned off and the diode 435 is turned on, the auxiliary windings 403A and 403B connected in series are connected to the capacitor 421a via the diode 424. As a result, the terminal voltage of the auxiliary windings 403A and 403B connected in series is fixed to the terminal voltage of the capacitor 421a. Therefore, the voltage between the terminals of the secondary windings 401A and 401B connected in series is fixed to a predetermined voltage determined by the voltage between the terminals of the capacitor 421a, the turn ratio of the transformer 40, and the on-duty ratio of the main switching element 420. Will be. Therefore, the reverse voltage applied to the diode 434 can be suppressed to a predetermined voltage determined by the voltage between the terminals of the capacitor 421a, the turn ratio, and the on-duty ratio.

  Next, the effect will be described. According to the fourth embodiment, the voltage between the terminals of the auxiliary windings 402A and 402B connected in series and the auxiliary windings 403A and 403B connected in series is fixed to the voltage of the battery B4 or the voltage between the terminals of the capacitor 421a. Therefore, the voltage between the terminals of the auxiliary windings 402A and 402B connected in series and the auxiliary windings 403A and 403B connected in series can be reliably fixed to a predetermined voltage.

  Further, according to the fourth embodiment, the auxiliary windings 402A and 402B connected in series via the diode 422b are connected to the battery B4. Further, the auxiliary windings 403A and 403B connected in series via the diode 424 are connected to the capacitor 421a. Therefore, the voltage between the terminals of the auxiliary windings 402A and 402B and the auxiliary windings 403A and 403B connected in series can be reliably fixed to the voltage of the battery B4 or the voltage between the terminals of the capacitor 421a.

  Furthermore, according to the fourth embodiment, the primary windings 400A and 400B and the auxiliary windings 402A, 402B, 403A, and 403B are set to have the same number of turns. Thus, the voltage between the terminals of the auxiliary windings 402A and 402B connected in series and the auxiliary windings 403A and 403B connected in series is made the same as the voltage between the terminals of the first windings 400A and 400B connected in series. Can do. Therefore, the diodes 422b and 424 can be reliably turned on.

(Fifth embodiment)
Next, a DC-DC converter according to a fifth embodiment will be described. The DC-DC converter according to the fifth embodiment deletes one of the active clamp circuit and the surge suppression circuit constituting the input side circuit from the DC-DC converter according to the first embodiment, and the diode constituting the output side circuit and The coil is deleted.

  First, the configuration of the DC-DC converter of the fifth embodiment will be described with reference to FIG. Here, FIG. 6 is a circuit diagram of the DC-DC converter in the fifth embodiment. Note that the symbol “·” attached to the primary winding 500, the secondary winding 501, and the auxiliary winding 502 of the transformer 50 indicates the start of winding of the winding.

  The DC-DC converter 5 (switching power supply device) shown in FIG. 6 is a one-stone flyback converter. The DC-DC converter 5 includes a transformer 50, a coil 51 input side circuit 52, an output side circuit 53, and a control circuit 54. The transformer 50, the coil 51, and the control circuit 54 have the same configuration as the transformer 10, the coil 11, and the control circuit 14 of the first embodiment.

  The input side circuit 52 includes a main switching element 520 (switching element), a surge suppression circuit 522, and an auxiliary winding 502. The input side circuit 52 has a configuration in which the active clamp circuit 12 and the surge suppression circuit 123 are deleted from the input side circuit 12 of the first embodiment.

  The output side circuit 53 includes a diode 530 (rectifier element) and a capacitor 533. The output side circuit 53 has a configuration in which the diode 131 and the coil 132 are deleted from the output side circuit 13 of the first embodiment.

  Next, the operation of the DC-DC converter will be described with reference to FIG. Note that the DC-DC converter 5 is a one-stone flyback converter as described above, and the voltage conversion operation is well known, and thus the description thereof is omitted. Here, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described.

  When the diode 530 is turned off, the auxiliary winding 502 is connected to the battery B5 via the diode 522b. As a result, the voltage between the terminals of the auxiliary winding 502 is fixed to the voltage of the battery B5. Therefore, the voltage between the terminals of the secondary winding 501 is fixed to a predetermined voltage determined by the voltage of the battery B5 and the turns ratio of the transformer 50. Therefore, the reverse voltage applied to the diode 530 can be suppressed to a predetermined voltage determined by the voltage of the battery B5 and the turn ratio.

  Next, the effect will be described. According to the fifth embodiment, the terminal voltage of the auxiliary winding 502 is fixed to the voltage of the battery B5. Therefore, the voltage between the terminals of the auxiliary winding 502 can be reliably fixed to a predetermined voltage.

  Furthermore, according to the fifth embodiment, the auxiliary winding 502 is connected to the battery B5 via the diode 522b. Therefore, the voltage between the terminals of the auxiliary winding 502 can be reliably fixed to the voltage of the battery B5.

(Sixth embodiment)
Next, a DC-DC converter according to a sixth embodiment will be described. First, the configuration of the DC-DC converter of the fifth embodiment will be described with reference to FIG. Here, FIG. 7 is a circuit diagram of the DC-DC converter in the sixth embodiment. In addition, the mark attached to the primary winding 600, the secondary windings 601 and 602, and the auxiliary windings 603 and 604 of the transformer 6 indicates the start of winding of the windings.

The DC-DC converter 6 (switching power supply device) shown in FIG. 7 is a full-bridge converter that insulates and steps down the DC voltage output from the battery B6 (DC power supply) and supplies it to the electronic device S6 mounted on the vehicle. is there. The DC-DC converter 6 includes a transformer 60, a coil 61, an input side circuit 62, an output side circuit 63, and a control circuit 64.

  The transformer 60 is an element that steps down an alternating voltage input to the primary side and outputs it from the secondary side. The transformer 60 includes a primary winding 600, a secondary winding 601 (first secondary winding), a secondary winding 602 (second secondary winding), and auxiliary windings 603 and 604. It has. The number of turns of the primary winding 600 is set to Np. The number of turns of the secondary windings 601 and 602 is set to Ns smaller than the number of turns Np of the primary winding 600. The number of turns of the auxiliary windings 603 and 604 is set to the same Np as the number of turns of the primary winding 600. One end on the winding start side of the primary winding 600 is connected to the coil 61, and the other end is connected to the input side circuit 62. The secondary windings 601 and 602 are connected in series. One end on the winding start side of the secondary winding 601 and one end on the winding end side of the secondary winding 602 are connected to the output side circuit 63, respectively. One end and the other end of the auxiliary windings 603 and 604 are connected to components of the input side circuit 62, respectively.

  The coil 61 is an element that stores and discharges energy when a current flows. The coil 61 is connected in series with the primary winding 600. One end of the coil 61 is connected to one end of the primary winding 600, and the other end is connected to the input side circuit 62.

  The input side circuit 62 is a circuit that converts a DC voltage output from the battery B6 into an AC voltage. The input side circuit 62 includes a switching circuit 620, a surge suppression diode 621 (first surge suppression rectifier element), 622 (second surge suppression rectifier element), a surge suppression capacitor 623 (surge suppression capacitor element), and an auxiliary winding. 603, 604.

  The switching circuit 620 is an element that is connected between the primary winding 600 and the battery B6 and controls the voltage supplied from the battery B6 to the primary winding 600 by switching. The switching circuit 620 includes switching elements 620a to 620d (first switching element to fourth switching element). The switching elements 620a to 620d are, for example, MOSFETs. The switching element 620a (first switching element), 620b (second switching element), the switching element 620c (third switching element), and 620d (fourth switching element) are connected in series. Specifically, the sources of the switching elements 620a and 620c are connected to the drains of the switching elements 620b and 620d, respectively. The switching elements 620a and 620b and the switching elements 620c and 620d connected in series are connected in parallel to the battery B6. Specifically, the drains of the switching elements 620a and 620c are connected to the positive terminal of the battery B6, and the sources of the switching elements 620b and 620d are connected to the negative terminal of the battery B6.

  The surge suppression diodes 621 and 622 and the surge suppression capacitor 623 are circuits that suppress a surge voltage generated in association with switching of the switching elements 620a to 620d.

  The surge suppression diode 621 is connected in series to the auxiliary winding 603. Specifically, the cathode of the surge suppression diode 621 is connected to one end on the winding start side of the auxiliary winding 603. The anode of the surge suppression diode 621 is connected to the source of the switching element 620a. The other end of the auxiliary winding 603 is connected to the drain of the switching element 620a. The surge suppression diode 621 and the auxiliary winding 603 connected in series are connected in parallel to the switching element 620a.

  The surge suppression diode 622 is connected in series with the auxiliary winding 604. Specifically, the cathode of the surge suppression diode 622 is connected to one end on the winding end side of the auxiliary winding 604. The anode of the surge suppression diode 622 is connected to the source of the switching element 620b. The other end of the auxiliary winding 604 is connected to the drain of the switching element 620b. The surge suppression diode 622 and the auxiliary winding 604 connected in series are connected in parallel to the switching element 620b.

  One end of the surge suppression capacitor 623 is connected to a connection point between the auxiliary winding 603 and the surge suppression diode 621, and the other end is connected to a connection point between the auxiliary winding 604 and the surge suppression diode 622.

The output side circuit 63 includes a diode 630 (first rectifier element), 631 (second rectifier element),
A coil 632 and a capacitor 633 are provided.

  The diode 630 is connected between one end of the secondary windings 601 and 602 connected in series and the positive end of the electronic device S6. The anode of the diode 630 is connected to one end on the winding start side of the secondary winding 601. The cathode is connected to the coil 632 and connected to the positive terminal of the electronic device S6 through the coil 632.

  The diode 632 is connected between the other end of the secondary windings 601 and 602 connected in series and the positive end of the electronic device S6. The anode of the diode 632 is connected to one end on the winding end side of the secondary winding 602. The cathode is connected to the coil 632 and connected to the positive terminal of the electronic device S6 through the coil 632.

  One end of the capacitor 633 is connected to the other end of the coil 632 connected to the positive terminal of the electronic device S6. The other end is connected to the connection point of the secondary windings 601 and 602 connected to the negative electrode end of the electronic device S6.

  The control circuit 64 is a circuit that controls switching of the switching elements 620a to 620d so that the output voltage becomes the target voltage. The control circuit 64 is connected to the gates of the switching elements 620a to 620d.

  Next, the operation of the DC-DC converter 6 will be described with reference to FIGS. Here, FIG. 8 is a waveform of each part of the DC-DC converter shown in FIG. Note that the DC-DC converter 6 is a full-bridge converter as described above, and the voltage conversion operation is well known, and thus the description thereof is omitted. Here, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described.

  When the switching elements 620a and 620d shown in FIG. 7 are turned on and the switching elements 620b and 620c are turned off, the diode 630 is turned on and the diode 631 is turned off. As shown in FIG. 8, the forward current flowing through the diode 630 increases and the forward current flowing through the diode 631 decreases (t0 to t1). When the forward current flowing through the diode 631 becomes 0 (t1), the diode 631 enters a reverse recovery period. However, the capacitor 623 and the coil 61 suppress a steep voltage change at the time of reverse recovery by the resonance operation. Therefore, the generation of noise can be suppressed.

  When the capacitor 623 is charged by the resonance operation with the coil 61, the diode 622 becomes conductive (t2 to t3). The auxiliary winding 604 is connected to the battery B6 via the switching element 620a and the diode 622. As a result, the terminal voltage of the auxiliary winding 604 is fixed to the voltage of the battery B6. Therefore, the voltage between the terminals of the secondary winding 602 is fixed to a predetermined voltage determined by the voltage of the battery B6 and the turn ratio of the transformer 60. Therefore, the reverse voltage applied to the diode 631 can be suppressed to a predetermined voltage determined by the voltage of the battery B6 and the turn ratio. At this time, the current flowing through the auxiliary winding 604 flows back through the coil 61, the primary winding 600, the switching element 620d, and the diode 622. The energy accumulated in the coil 61 by the resonance operation with the capacitor 623 is finally transferred to the output side circuit 63 via the transformer 60.

  When the switching elements 620a and 620c shown in FIG. 7 are turned on and the switching elements 620b and 620d are turned off, the energy accumulated in the capacitor 623 by the resonance operation is transferred to the coil 61 (t3 to t4). The energy stored in the capacitor 623 finally acts in a direction to reduce the circulating current passing through the coil 61, the primary winding 600, the switching element 620c, and the switching element 620a, and the switching elements 620a and 620c. The conduction loss can be reduced (t4 to t5).

  When the switching elements 620b and 620c shown in FIG. 7 are turned on and the switching elements 620a and 620d are turned off, the diode 630 is turned off and the diode 631 is turned on. As shown in FIG. 8, the forward current flowing through the diode 630 decreases and the forward current flowing through the diode 631 increases (t4 to t5). When the forward current flowing through the diode 630 becomes 0 (t5), the diode 630 enters a reverse recovery period. However, the capacitor 623 and the coil 61 suppress a steep voltage change at the time of reverse recovery by the resonance operation. Therefore, the generation of noise can be suppressed.

  When the capacitor 623 is charged by the resonance operation with the coil 61, the diode 621 becomes conductive (t7 to t8). The auxiliary winding 603 is connected to the battery B6 through the switching element 620b and the diode 621. As a result, the terminal voltage of the auxiliary winding 603 is fixed to the voltage of the battery B6. Therefore, the voltage between the terminals of the secondary winding 601 is fixed to a predetermined voltage determined by the voltage of the battery B6 and the turn ratio of the transformer 60. Therefore, the reverse voltage applied to the diode 630 can be suppressed to a predetermined voltage determined by the voltage of the battery B6 and the turn ratio. At this time, the current flowing through the auxiliary winding 603 flows back through the switching element 620c, the primary winding 600, the coil 61, and the diode 621. The energy accumulated in the coil 61 by the resonance operation with the capacitor 623 is finally transferred to the output side circuit 63 via the transformer 60.

  When the switching elements 620b and 620d shown in FIG. 7 are turned on and the switching elements 620a and 620c are turned off, the energy accumulated in the capacitor 623 by the resonance operation is transferred to the coil 61 (t8 to t9). The energy accumulated in the capacitor 623 finally acts in a direction to reduce the circulating current passing through the coil 61, the switching element 620b, the switching element 620d, and the primary winding 600, and the switching elements 620b and 620d. The conduction loss can be reduced (t9 to t10).

  Next, the effect will be described. According to the sixth embodiment, the voltage between the terminals of the auxiliary windings 603 and 604 is fixed to the voltage of the battery B6. Therefore, the voltage between the terminals of the auxiliary windings 603 and 603 can be reliably fixed.

  Further, according to the sixth embodiment, the auxiliary winding 603 is connected to the battery B6 via the switching element 620b and the diode 621. Further, the auxiliary winding 604 is connected to the battery B6 through the switching element 620a and the diode 622. Therefore, auxiliary windings 603 and 604 can be reliably fixed to the voltage of battery B6.

  Furthermore, according to the sixth embodiment, the primary winding 600 and the auxiliary windings 603 and 604 are set to have the same number of turns. Thereby, the voltage between the terminals of the auxiliary windings 603 and 604 can be made the same as the voltage between the terminals of the first winding 600. Therefore, the diodes 621 and 622 can be surely brought into conduction.

(Seventh embodiment)
Next, a DC-DC converter according to a seventh embodiment will be described. The DC-DC converter of 7th Embodiment changes the structure of a surge suppression circuit with respect to the DC-DC converter of 6th Embodiment.

  First, the configuration of the DC-DC converter of the seventh embodiment will be described with reference to FIG. Here, FIG. 9 is a circuit diagram of the DC-DC converter in the seventh embodiment. Note that the symbol “·” attached to the primary winding 700, the secondary windings 701 and 702, and the auxiliary windings 703 and 704 of the transformer 7 indicates the start of winding of the winding.

  A DC-DC converter 7 (switching power supply device) shown in FIG. 9 is a full-bridge converter. The DC-DC converter 7 includes a transformer 70, a coil 71, an input side circuit 72, an output side circuit 73, and a control circuit 74. The transformer 70, coil 71, output side circuit 73, and control circuit 74 have the same configuration as the transformer 60, coil 61, output side circuit 63, and control circuit 64 of the sixth embodiment.

  The input side circuit 72 includes a switching circuit 720, a surge suppression diode 721 (first surge suppression rectifier element), 722 (second surge suppression rectifier element), a surge suppression capacitor 723 (surge suppression capacitor element), and an auxiliary winding. 703 and 704. The switching circuit 720 has the same configuration as the switching circuit 620 of the sixth embodiment.

  The surge suppression diode 721 is connected in series to the auxiliary winding 703. Specifically, the cathode of the surge suppression diode 721 is connected to one end on the winding start side of the auxiliary winding 703. The anode of the surge suppression diode 721 is connected to the negative terminal of the battery B7. The other end of the auxiliary winding 703 is connected to the positive end of the battery B7. The surge suppression diode 721 and the auxiliary winding 703 connected in series are connected in parallel to the battery B7.

  The surge suppression diode 722 is connected in series to the auxiliary winding 704. Specifically, the cathode of the surge suppression diode 722 is connected to one end on the winding end side of the auxiliary winding 704. The anode of the surge suppression diode 722 is connected to the negative terminal of the battery B7. The other end of the auxiliary winding 704 is connected to the positive end of the battery B7. The surge suppression diode 722 and the auxiliary winding 704 connected in series are connected in parallel to the battery B7.

  Next, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described with reference to FIG. When the diode 730 is turned on and the diode 731 is turned off, the auxiliary winding 704 is connected to the battery B7 via the diode 722. As a result, the voltage between the terminals of the auxiliary winding 704 is fixed to the voltage of the battery B7. Therefore, the voltage between the terminals of the secondary winding 702 is fixed to a predetermined voltage determined by the voltage of the battery B7 and the turn ratio of the transformer 70. Therefore, the reverse voltage applied to the diode 731 can be suppressed to a predetermined voltage determined by the voltage of the battery B7 and the turn ratio.

  When the diode 730 is turned off and the diode 731 is turned on, the auxiliary winding 703 is connected to the battery B7 via the diode 721. As a result, the voltage between the terminals of the auxiliary winding 703 is fixed to the voltage of the battery B7. Therefore, the voltage between the terminals of the secondary winding 701 is fixed to a predetermined voltage determined by the voltage of the battery B7 and the turn ratio of the transformer 70. Therefore, the reverse voltage applied to the diode 730 can be suppressed to a predetermined voltage determined by the voltage of the battery B7 and the turn ratio.

  Next, the effect will be described. According to the seventh embodiment, the auxiliary winding 703 is connected to the battery B7 via the diode 721. Further, the auxiliary winding 704 is connected to the battery B7 via the diode 722. Therefore, the auxiliary windings 703 and 704 can be reliably fixed to the voltage of the battery B7.

  In the seventh embodiment, an example in which the surge suppression diode 721 and the auxiliary winding 703 connected in series, and the surge suppression diode 722 and the auxiliary winding 704 connected in series are connected in parallel to the battery B7. However, it is not limited to this.

  As shown in FIG. 10, the surge suppression diode 721 and the auxiliary winding 703 connected in series are connected in parallel to the switching element 720d, and the surge suppression diode 722 and the auxiliary winding 704 connected in series are connected in parallel to the switching element 720b. It may be. According to this configuration, the auxiliary winding 703 is connected to the battery B7 via the switching element 720c and the diode 721. Further, the auxiliary winding 704 is connected to the battery B7 through the switching element 720a and the diode 722. Therefore, the auxiliary windings 703 and 704 can be reliably fixed to the voltage of the battery B7.

  Further, as shown in FIG. 11, the surge suppression diode 721 and the auxiliary winding 703 connected in series are connected in parallel to the battery B7, and the surge suppression diode 722 and the auxiliary winding 704 connected in series are connected in parallel to the switching element 720b. May be. According to this configuration, the auxiliary winding 703 is connected to the battery B7 via the diode 721. Further, the auxiliary winding 704 is connected to the battery B7 through the switching element 720a and the diode 722. Therefore, the auxiliary windings 703 and 704 can be reliably fixed to the voltage of the battery B7.

  It is sufficient that at least one of the auxiliary windings 703 and 704 is fixed to the voltage of the battery B7 when the diodes 730 and 731 are not conductive.

(Eighth embodiment)
Next, a DC-DC converter according to an eighth embodiment will be described. The DC-DC converter of the eighth embodiment is obtained by changing the configuration of the surge suppression circuit with respect to the DC-DC converter of the sixth embodiment, and accordingly changing the number of turns of the auxiliary winding.

  First, the configuration of the DC-DC converter of the eighth embodiment will be described with reference to FIG. Here, FIG. 12 is a circuit diagram of the DC-DC converter in the eighth embodiment. Note that the symbol “·” attached to the primary winding 800, the secondary windings 801 and 802, and the auxiliary windings 803 and 804 of the transformer 8 indicates the beginning of winding.

  The DC-DC converter 8 (switching power supply device) shown in FIG. 12 is a full bridge converter. The DC-DC converter 8 includes a transformer 80, a coil 81, an input side circuit 82, an output side circuit 83, and a control circuit 84. The coil 81, the output side circuit 83, and the control circuit 84 have the same configuration as the transformer 60, the output side circuit 63, and the control circuit 64 of the sixth embodiment.

  The transformer 80 includes a primary winding 800, a secondary winding 801 (first secondary winding), a secondary winding 802 (second secondary winding), and auxiliary windings 803 and 804. It has. The number of turns of the primary winding 800 is set to Np. The number of turns of the secondary windings 801 and 802 is set to Ns smaller than the number of turns Np of the primary winding 800. The number of turns of the auxiliary windings 803 and 804 is set to Np / 2 which is ½ of the number of turns of the primary winding 800. One end on the winding start side of the primary winding 800 is connected to the coil 81, and the other end is connected to the input side circuit 82. The secondary windings 801 and 802 are connected in series. One end on the winding start side of the secondary winding 801 and one end on the winding end side of the secondary winding 802 are connected to the output side circuit 83, respectively. One end and the other end of the auxiliary windings 803 and 804 are connected to components of the input side circuit 82, respectively.

  The input side circuit 82 includes a switching circuit 820, a surge suppression diode 821 (first surge suppression rectifier element), 822 (second surge suppression rectifier element), a surge suppression capacitor 823 (third surge suppression capacitor element), a surge Suppression capacitors 824 (first surge suppression capacitance elements) and 825 (second surge suppression capacitance elements) and auxiliary windings 803 and 804 are provided. The switching circuit 820 has the same configuration as the switching circuit 620 of the sixth embodiment.

  Surge suppression capacitors 824 and 825 are connected in series. One end of the surge suppression capacitor 824 is connected to the positive terminal of the battery B8. One end of the surge suppression capacitor 825 is connected to the negative end of the battery B8.

  The surge suppression diode 821 is connected in series to the auxiliary winding 803. Specifically, the cathode of the surge suppression diode 821 is connected to one end on the winding start side of the auxiliary winding 803. The anode of the surge suppression diode 821 is connected to the connection point of the surge suppression capacitors 824 and 825. The other end of the auxiliary winding 803 is connected to one end of a surge suppression capacitor 824. The surge suppression diode 821 and the auxiliary winding 803 connected in series are connected in parallel to the surge suppression capacitor 824.

  The surge suppression diode 822 is connected in series with the auxiliary winding 804. Specifically, the cathode of the surge suppression diode 822 is connected to one end on the winding end side of the auxiliary winding 803. The anode of the surge suppression diode 822 is connected to one end of the surge suppression capacitor 825. The other end of the auxiliary winding 804 is connected to a connection point between the surge suppression capacitors 824 and 825. The surge suppression diode 822 and the auxiliary winding 804 connected in series are connected in parallel to the surge suppression capacitor 825.

  Next, the operation of reducing the reverse voltage applied to the diode constituting the output side circuit will be described with reference to FIG. When the diode 830 is turned on and the diode 831 is turned off, the auxiliary winding 804 is connected to the surge suppression capacitor 825 via the diode 822. As a result, the voltage between the terminals of the auxiliary winding 804 is fixed to the voltage of the surge suppression capacitor 825. Therefore, the voltage between the terminals of the secondary winding 802 is fixed to a predetermined voltage determined by the voltage of the surge suppression capacitor 825 and the turn ratio of the transformer 80. Therefore, the reverse voltage applied to the diode 831 can be suppressed to a predetermined voltage determined by the voltage of the surge suppression capacitor 825 and the turn ratio.

  When the diode 830 is turned off and the diode 831 is turned on, the auxiliary winding 803 is connected to the surge suppression capacitor 824 via the diode 821. As a result, the terminal voltage of the auxiliary winding 803 is fixed to the voltage of the surge suppression capacitor 824. Therefore, the voltage across the secondary winding 801 is fixed to a predetermined voltage determined by the voltage of the surge suppression capacitor 824 and the turn ratio of the transformer 80. Therefore, the reverse voltage applied to the diode 830 can be suppressed to a predetermined voltage determined by the voltage of the surge suppression capacitor 824 and the turn ratio.

  Next, the effect will be described. According to the eighth embodiment, the auxiliary winding 803 is connected to the surge suppression capacitor 824 via the diode 824. Further, the auxiliary winding 804 is connected to the surge suppression capacitor 825 via the diode 825. Therefore, the auxiliary windings 803 and 804 can be reliably fixed to the voltage of the surge suppression capacitors 824 and 825.

  Further, according to the eighth embodiment, the number of turns of the auxiliary windings 803 and 804 is set to be ½ of the number of turns of the primary winding 800. Thereby, the voltage between the terminals of the auxiliary windings 803 and 804 can be made the same as the voltage between the terminals of the first winding 800. Therefore, the diodes 821 and 822 can be reliably turned on.

1-8 ... DC-DC converter 10, 20, 30A, 30B, 40A, 40B, 50, 60, 70, 80 ... Transformer, 100, 200, 300A, 300B, 400A, 400B, 500, 600 700, 800 ... primary winding, 101, 201, 301A, 301B, 401A, 401B, 501, 601, 701, 801 ... secondary winding, 102, 202, 203, 302A, 302B, 402A , 402B, 403A, 403B, 502, 603, 604, 703, 704, 803, 804 ... auxiliary winding, 11, 21, 51, 61, 71, 81 ... coil, 12, 22, 32, 42 , 52, 62, 72, 82... Input side circuit, 120, 220. 320, 420, 520,... Main switching element, 121, 221 321, 421, 521... Active clamp circuit, 121 a, 221 a, 321 a, 421 a, 521 a... Capacitor, 121 b, 221 b, 321 b, 421 b, 521 b. 422, 522 ... Surge suppression circuit, 122a, 123a, 222a, 322a, 323a, 422a, 522a ... Capacitor, 122b, 123b, 322b, 323b, 422b, 522b ... Diode, 222b, 224, 424, 621, 622, 721, 722, 821, 822 ... Surge suppression diode, 225, 425, 623, 723, 823-825 ... Surge suppression capacitor, 620, 720, 820 ... Switching circuit, 620a-620d , 7 0a to 720d, 820a to 820d... Switching element, 13, 23, 33, 43, 53, 63, 73, 83... Output side circuit, 130, 131, 230, 231, 334, 335, 434, 435 530, 630, 631, 730, 731, 830, 831 ... diode, 132, 232, 732, 832 ... coil, 133, 233, 333, 433, 533, 633, 733, 833 ... capacitor , 14, 24, 34, 44, 54, 64, 74, 84... Control circuit, B1 to B8... Battery, S1 to S8.

Claims (24)

A transformer having a primary winding and a secondary winding;
A switching element connected between the primary winding and a DC power source;
A rectifying element connected between the secondary winding and a load;
In a switching power supply device comprising:
The transformer includes an auxiliary winding, and a voltage between terminals of the auxiliary winding is fixed to a predetermined voltage when the rectifying element is non-conductive.   2. The switching power supply device according to claim 1, wherein a voltage between the terminals of the auxiliary winding is fixed to a voltage of the DC power supply when the rectifying element is non-conductive. 3.   A surge suppression capacitor element and a surge suppression rectifier element are connected in parallel, and are connected in series to the auxiliary winding, and have a surge suppression circuit connected in parallel to the DC power source in a state of being connected in series. The switching power supply device according to claim 2. The rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element is connected between one end of the secondary winding and one end of the load. Is connected between the other end of the secondary winding and one end of the load,
A clamp capacitor element and a clamp switching element connected in series, and having an active clamp circuit connected in parallel to the primary winding;
The terminal voltage of the auxiliary winding is fixed to the voltage of the DC power supply when the second rectifier element is non-conductive, and is fixed to the terminal voltage of the clamp capacitor element when the first rectifier element is non-conductive. The switching power supply device according to claim 1. A first surge suppression circuit configured by connecting a first surge suppression capacitor element and a first surge suppression rectifier element in parallel, connected in series to the auxiliary winding, and connected in parallel to the DC power source in a state of being connected in series; ,
A second surge suppression capacitor element and a second surge suppression rectifier element connected in parallel; a connection point between the auxiliary winding and the first surge suppression circuit; a connection point between the clamp capacitor element and the clamp switching element; A second surge suppression circuit connected between
The switching power supply device according to claim 4, comprising:   6. The switching power supply device according to claim 3, wherein the primary winding and the auxiliary winding have the same number of turns. The auxiliary winding comprises a first auxiliary winding and a second auxiliary winding,
The rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element is connected between one end of the secondary winding and one end of the load. Is connected between the other end of the secondary winding and one end of the load,
A clamp capacitor element and a clamp switching element connected in series, and having an active clamp circuit connected in parallel to the primary winding;
The voltage between the terminals of the first auxiliary winding is fixed to the voltage of the DC power supply when the second rectifying element is non-conductive, and the voltage between the terminals of the second auxiliary winding is non-conductive with the first rectifying element. The switching power supply device according to claim 1, wherein the switching power supply device is fixed to a voltage between terminals of the clamp capacitor element when conducting. A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to a DC power source in a state of being connected in series;
A second surge suppression rectifier element connected in series to the second auxiliary winding and connected in parallel to the clamp capacitor element in a connected state;
A second surge suppression capacitive element connected between a connection point of the first auxiliary winding and the surge suppression circuit, and a connection point of the second auxiliary winding and the second surge suppression rectifier element;
The switching power supply device according to claim 7, comprising:   The switching power supply according to claim 8, wherein the primary winding, the first auxiliary winding, and the second auxiliary winding have the same number of turns. The transformer includes a first transformer and a second transformer,
The primary winding, the secondary winding and the auxiliary winding of the first transformer and the second transformer are respectively connected in series,
The switching element is connected between the primary winding and the DC power source of the first transformer and the second transformer connected in series,
The rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element includes the first transformer connected in series, one end of the secondary winding of the second transformer, and the load. The second rectifying element is connected between the first transformer and the other end of the secondary winding of the second transformer and one end of the load connected in series.
An active clamp circuit configured by connecting a clamp capacitor and a clamp switching element in series, and connected in parallel to the primary winding of the first transformer and the second transformer connected in series;
The voltage between the terminals of the auxiliary windings of the first transformer and the second transformer connected in series is fixed to the voltage of the DC power supply when the second rectifier element is non-conductive, and the voltage of the first rectifier element is non-conductive. The switching power supply device according to claim 1, wherein the switching power supply device is fixed to a voltage between terminals of the clamp capacitor element when conducting. The first surge suppression capacitor element and the first surge suppression rectifier element are connected in parallel, and are connected in series to the auxiliary windings of the first transformer and the second transformer connected in series, and in a state of being connected in series. A first surge suppression circuit connected in parallel to the DC power supply;
A first surge suppression capacitor element and a second surge suppression rectifier element are connected in parallel, and the first transformer, the auxiliary winding of the second transformer, and the connection point of the first surge suppression circuit are connected in series. A second surge suppression circuit connected between the clamp capacitor element and a connection point of the clamp switching element;
The switching power supply device according to claim 10, comprising:   The switching power supply according to claim 11, wherein the number of turns of the primary winding and the auxiliary winding of the first transformer and the second transformer is the same. The transformer includes a first transformer and a second transformer,
The auxiliary winding comprises a first auxiliary winding and a second auxiliary winding,
The primary winding, the secondary winding, the first auxiliary winding, and the second auxiliary winding of the first transformer and the second transformer are connected in series, respectively.
The switching element is connected between the first transformer and the primary winding of the second transformer connected in series, and the DC power supply,
The rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element includes the first transformer and one end of the secondary winding of the second transformer connected in series; The second rectifying element is connected between one end of the load, and the second rectifying element is connected between the other end of the secondary winding of the first transformer and the second transformer connected in series and one end of the load. And
An active clamp circuit configured by connecting a clamp capacitor and a clamp switching element in series, and connected in parallel to the primary winding of the first transformer and the second transformer connected in series;
The voltage between the terminals of the first auxiliary winding of the first transformer and the second transformer connected in series is fixed to the voltage of the DC power supply when the second rectifying element is non-conductive, and the voltage of the first transformer is connected in series. The terminal voltage of the second auxiliary winding of the first transformer and the second transformer is fixed to the terminal voltage of the clamp capacitor element when the first rectifier element is non-conductive. The switching power supply device according to 1. The first surge suppression capacitance element and the first surge suppression rectifier element are connected in parallel, and are connected in series to the first auxiliary winding of the first transformer and the second transformer connected in series, and connected in series. A surge suppression circuit connected in parallel to the DC power supply in a state;
A second surge suppression rectifier element connected in series to the second auxiliary winding of the first transformer and the second transformer connected in series, and connected in parallel to the clamp capacitor element in a connected state;
The first auxiliary winding of the first transformer and the second transformer connected in series and the connection point of the surge suppression circuit, and the second auxiliary winding of the first transformer and the second transformer connected in series And a second surge suppression capacitive element connected between a connection point of the second surge suppression rectifier element,
The switching power supply device according to claim 13, comprising: The switching power supply according to claim 14, wherein the number of turns of the primary winding, the first auxiliary winding, and the second auxiliary winding of the first transformer and the second transformer is the same. The secondary winding includes a first secondary winding and a second secondary winding, and the first secondary winding and the second secondary winding are connected in series,
The auxiliary winding comprises a first auxiliary winding and a second auxiliary winding,
The rectifying element includes a first rectifying element and a second rectifying element, and the first rectifying element is connected between one end of the first secondary winding and one end of the load. The two rectifying elements are connected between one end of the second secondary winding and one end of the load,
At least one of the inter-terminal voltages of the first auxiliary winding and the second auxiliary winding is fixed to the voltage of the DC power supply when the first rectifying element and the second rectifying element are non-conductive. The switching power supply device according to claim 1, wherein The switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power source in a state of being connected in series, and the third switching element and The fourth switching element is connected in parallel to the DC power supply in a state of being connected in series,
The primary winding is connected between a connection point of the first switching element and the second switching element, and a connection point of the third switching element and the fourth switching element,
A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to the first switching element in a state of being connected in series;
A second surge suppression rectifier element connected in series with the second auxiliary winding and connected in parallel to the second switching element in a state of being connected in series;
A surge suppression capacitive element connected between a connection point of the first auxiliary winding and the first surge suppression rectifying element, and a connection point of the second auxiliary winding and the second surge suppression rectification element;
The switching power supply device according to claim 16, comprising: The switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power source in a state of being connected in series, and the third switching element and The fourth switching element is connected in parallel to the DC power supply in a state of being connected in series,
The primary winding is connected between a connection point of the first switching element and the second switching element, and a connection point of the third switching element and the fourth switching element,
A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to the DC power supply in a state of being connected in series;
A second surge suppression rectifier element connected in series to the second auxiliary winding and connected in parallel to the DC power source in a state of being connected in series;
A surge suppression capacitive element connected between a connection point of the first auxiliary winding and the first surge suppression rectifying element, and a connection point of the second auxiliary winding and the second surge suppression rectification element;
The switching power supply device according to claim 16, comprising: The switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power source in a state of being connected in series, and the third switching element and The fourth switching element is connected in parallel to the DC power supply in a state of being connected in series,
The primary winding is connected between a connection point of the first switching element and the second switching element, and a connection point of the third switching element and the fourth switching element,
A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to the fourth switching element in a state of being connected in series;
A second surge suppression rectifier element connected in series with the second auxiliary winding and connected in parallel to the second switching element in a state of being connected in series;
A surge suppression capacitive element connected between a connection point of the first auxiliary winding and the first surge suppression rectifying element, and a connection point of the second auxiliary winding and the second surge suppression rectification element;
The switching power supply device according to claim 16, comprising: The switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power source in a state of being connected in series, and the third switching element and The fourth switching element is connected in parallel to the DC power supply in a state of being connected in series,
The primary winding is connected between a connection point of the first switching element and the second switching element, and a connection point of the third switching element and the fourth switching element,
A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to the DC power supply in a state of being connected in series;
A second surge suppression rectifier element connected in series with the second auxiliary winding and connected in parallel to the second switching element in a state of being connected in series;
A surge suppression capacitive element connected between a connection point of the first auxiliary winding and the first surge suppression rectifying element, and a connection point of the second auxiliary winding and the second surge suppression rectification element;
The switching power supply device according to claim 16, comprising: The switching element includes a first switching element to a fourth switching element, and the first switching element and the second switching element are connected in parallel to the DC power source in a state of being connected in series, and the third switching element and The fourth switching element is connected in parallel to the DC power supply in a state of being connected in series,
The primary winding is connected between a connection point of the first switching element and the second switching element, and a connection point of the third switching element and the fourth switching element,
A first surge suppression capacitor element and a second surge suppression capacitor element connected in parallel to the DC power supply in a state of being connected in series;
A first surge suppression rectifier element connected in series to the first auxiliary winding and connected in parallel to the first surge suppression capacitor element in a connected state;
A second surge suppression rectifier element connected in series to the second auxiliary winding and connected in parallel to the second surge suppression capacitor element in a connected state;
A surge suppression capacitive element connected between a connection point of the first auxiliary winding and the first surge suppression rectifying element, and a connection point of the second auxiliary winding and the second surge suppression rectification element;
The switching power supply device according to claim 1, comprising: The switching power supply according to any one of claims 17 to 20, wherein the primary winding, the first auxiliary winding, and the second auxiliary winding have the same number of turns.   The switching power supply according to claim 21, wherein the number of turns of the first auxiliary winding and the second auxiliary winding is ½ of the number of turns of the primary winding. The switching power supply device according to any one of claims 1 to 23, wherein the switching power supply device is mounted on a vehicle and supplies a voltage to an electronic device.

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